Why the World Banned Chemical Weapons

On the late afternoon of April 22, 1915—in the midst of World War I—Algerian and French soldiers in trenches along the Western Front, near the Belgian town of Ypres, noticed a yellowish-green fog drifting toward them. Believing the cloud masked advancing German infantrymen, the soldiers prepared for an attack. In fact, the cloud was chlorine gas, released by the Germans from 6,000 pressurized cylinders. The gas crept forward, then lapped into the allied trenches in a ghostly tide. The effect was immediate: Thousands of soldiers choked and clutched at their throats, unable to breathe, before falling dead; thousands more fled in panic, opening a four-mile gap in the allied lines.

The Ypres attack was not the first time gas was used in the conflict (both the French and Germans had used tear gas earlier in the war), but it was the first time in the conflict that a poisonous gas was used in mass quantities. The effects of the attack were horrific, causing “a burning sensation in the head, red-hot needles in the lungs, the throat seized as by a strangler,” as one soldier later described it. More than 5,000 soldiers were killed in this first gas attack, while thousands more, stumbling to the rear and frothing at the mouth, suffered the debilitating aftereffects for decades.

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What took place earlier this month, in Syria’s Idlib province, had the same effect as the gas used at Ypres, as Syrian-flown SU-22 jets released bombs filled with sarin gas near the town of Khan Shaykhun. The attack killed dozens of Syrian civilians, including 11 children. The effects of the sarin, a deadly nerve agent, were similar to those of 1915: The victims choked and vomited as their lungs constricted, then suffered through tormenting muscle spasms and eventual death.

In both cases, the use of gas was nearly universally condemned. After the Ypres attack became public knowledge, London’s Daily Mirror issued a banner headline describing the horror—“Devilry, Thy Name Is Germany”—then repeated the theme in bold type more than 100 years later, after Khan Shaykhun: “Assad Gassing Kids Again.” The “again” was a not-so-veiled editorial comment, for Khan Shaykhun marked the second time Assad had used sarin to kill civilians; the first incident took place in August 2013, when the Syrian regime used the nerve agent in an attack on Ghouta, a suburb of Damascus, killing an estimated 281 to 1,700 civilians (the numbers remain uncertain) while injuring thousands. The pictures of the victims, caught in the throes of their final moments, shocked the world.

President Donald Trump, who hadn’t previously shown much concern for Syrian civilians, said the April 4 gas attack had changed his “attitude” toward Assad, and he ordered a missile strike on the airfield where the sarin had been stored. Trump’s turnabout stunned many observers, and it prompted some to wonder why, exactly, chemical weapons triggered a U.S. response when the vast majority of the half-million or so Syrians who have died in the country’s civil war were slaughtered by conventional means. Why, in other words, do we ban chemical weapons, but not equally deadly weapons like machine guns that rip through bodies and barrel bombs that tear them apart?

One answer is that while gas attacks are terrifying, the weapon has proved to be militarily ineffective. After Ypres, the allies provided masks to their front-line troops, who stood in their trenches killing onrushing Germans as clouds of gas enveloped their legs. That was true even as both sides climbed the escalatory ladder, introducing increasingly lethal chemicals (phosgene and mustard gas), that were then matched by increasingly effective countermeasures. The weapon also proved difficult to control. In several well-documented instances, gasses deployed by front-line troops blew back onto their own trenches—giving a literalist tinge to the term “blowback,” now used to describe the unintended consequences of an intelligence operation.

At the end of World War I, a precise tabulation of casualties showed that some 91,000 soldiers on all sides were killed in gas attacks—less than 10 percent of the total deaths for the entire war. Machine guns and artillery shells, it turns out, were far more effective systems for delivering death. But those numbers tell only a part of the story. The use of gas had enormous psychological consequences, adding a touch of barbarity to the already barbarous butchery. Poet Wilfred Owen’s “Dulce et Decorum est,” which described a gas attack, became the war’s iconic poem (“if you could hear, at every jolt, the blood Come gargling from the froth-corrupted lungs, Obscene as cancer ...”), while painter John Singer Sargent’s “Gassed” shows a line of soldiers, blinded by gas, stumbling forward in a kind of religious procession. The painting was attacked for its patriotism, but its message might have been too subtle for its critics, with the blind leading the blind through a blighted landscape. Long after the war, French veterans of the war’s mustard gas attacks could be seen, their faces pockmarked by scars from the burning blisters, in seats set aside for them on the Paris Metro—“pour les invalides de la grande guerre.”

Then too, while the Great War’s military commanders conceded that the effectiveness of poison gas was exaggerated, that didn’t keep them from using it. The German attack at Ypres lowered civilization’s bar, but the British and French quickly stooped to clear it. Sir John French, the British commander on the Western Front, harumphed his rage at the Germans, calling the Ypres attack “a cynical and barbarous disregard of the well-known usages of civilized war,” then quickly followed suit. “Owing to the repeated use by the enemy of asphyxiating gases in their attacks on our positions,” he announced, “I have been compelled to resort to similar methods.” Even so, there was little doubt that the use of poison gas was a kind of crime, or perhaps, as one British military officer later noted, “not quite cricket.”

After the war, the great powers agreed that the use of poison gas was wrong, but didn’t banish it outright. In 1925, the Geneva Protocol prohibited the “Use in War of Asphyxiating, Poisonous or other Gases, and of Bacteriological Methods of Warfare.” The agreement was signed most prominently by those who had used gas in the Great War—Austria, Britain, France, Germany and Russia (the U.S. signed the protocol, but the Senate did not ratify it until 1975). The protocol was widely hailed as recognition by the international community that some weapons were too horrible to use, even in war. But, manifestly, the treaty did not ban the production or stockpiling of gas or chemical weapons (as a kind of unstated “just in case” clause), and most of the major signatories to the agreement continued to develop increasingly lethal poison gas weapons.

Nor, as it turns out, did the stigma attached to the use of gas prohibit its use in the conflicts that followed. There were widespread reports that the British used gas against the Kurds during a 1920 uprising in Iraq. While the reports remain unconfirmed, the war secretary at the time—Winston Churchill—favored it. “I do not understand this squemishness about the use of gas,” he said. “I am strongly in favour of using poisoned gas against uncivilized tribes.” Benito Mussolini agreed. In late 1935, he approved the use of mustard gas by the Italian army during its invasion of Ethiopia. The attacks that followed resulted in more than 100,000 casualties. The unstated “just in case” clause was also quietly prominent during World War II. In 1944, Churchill, by then prime minister, urged his military commanders to “think very seriously over this question of poison gas.” It is “absurd,” Churchill went on to say, “to consider morality on this topic when everybody used it in the last war without a word of complaint from the moralists or the Church.” And Churchill went further, saying the only reason the Germans hadn’t used poison gas against allied troops was because they feared retaliation.

In light of White House spokesman Sean Spicer’s recent gaffe saying that “even Hitler” had not stooped to Assad’s use of chemical weapons (a breathtaking lapse that ignored Hitler’s use of gas to murder millions of Jews during the Holocaust and for which Spicer abjectly apologized), it’s worth revisiting the issue. Over the years, any number of explanations have been put forward for Hitler’s unwillingness to use gas as a battlefield weapon, including the hypothesis that having been gassed himself in World War I, he did not want to visit the same horror on others. That seems unlikely, to say the least. It’s more plausible that Hitler and his commanders understood the weapons’ battlefield limitations.

Whatever was really behind Hitler’s reluctance, it confirms what advocates for the banning of certain classes of weapons have suspected for years—that the world’s militaries are loath to ban weapons that kill effectively, while acceding to bans of weapons that they don’t need. Put another way, military leaders agreed to the banning of poison gas in 1925 not because it was horrifyingly effective, but because it wasn’t.

“It is a fickle weapon that can be turned on the attacker,” says retired Army Col. Paul Hughes, who served as a senior staff officer at the Pentagon’s Office of Reconstruction and Humanitarian Assistance. “So it was easy to negotiate its ban because it wasn’t as effective as conventional artillery.” But Hughes disagrees with the notion that the military will agree to ban only a weapon that is ineffective, pointing out that the U.S. military “eliminated all of its nuclear artillery rounds and its family of nuclear-capable intermediate range missiles, even though both would have been useful in a fight with the USSR.”

Even so, the U.S. military dug in its heels on two weapons systems that have been the focus of international efforts to ban them. In the mid-1990s, the military opposed a ban on land mines, despite strong support for outlawing them among a powerful group of retired senior military officers and a coalition of U.S. nongovernmental organizations. The issue then was whether U.S. “smart mines” (which turn themselves off after a prescribed period) could be removed from the U.S. arsenal, and whether the American army needed mines in South Korea, where they are stockpiled for use against an invasion by North Korea. Additionally, key senior military officers believed agreeing to the ban would set a dangerous precedent—that the military could be pressured into banning weapons by what they described as left-leaning humanitarian organizations. The view was reflected in a legendary exchange between then-Army Chief of Staff Eric Shinseki, who’d lost a foot to a land mine in Vietnam, and Sen. Patrick Leahy—who led the ban effort. Their exchange took place during a meeting on Capitol Hill. “We don’t want them and we don’t need them,” Shinseki said, “and we’re not going to get rid of them.”

The U.S. has also resisted efforts to ban cluster munitions—bombs that contain vicious bomblets that spread over a wide area. Cluster munitions were widely used during the Clinton administration’s war in the Balkans, but left the battlefield littered with bomblets that had failed to explode and so continued to kill and maim long after the war was concluded. The ban efforts began with a meeting of international delegates in Switzerland in the late 1990s, during which a coalition of delegates argued for and against a ban. Among the ban supporters was a Norwegian Foreign Ministry official who issued an impassioned plea for the adoption of a treaty banning the weapon. In the midst of his talk (which I attended), a British colonel leaned across the table at which I was sitting, a wry smile on his face. “You know why the Norwegians favor a ban?” he asked. I shook my head: no. “Because they don’t have any,” he said.

The British colonel had it just right: The world’s militaries don’t want to ban weapons that are efficient killers. So while it is true that the land mine and cluster munitions bans have gained widespread international support (162 countries have signed the land-mine ban, 108 countries have signed onto the Convention on Cluster Munitions), the countries most likely to use both (the U.S., China, Russia and India) remain nonsignatories. In the parlance of those working on these bans, the weapons have not yet been fully “stigmatized.”

But that’s not true for the ban on poison gas, which traces its long history from that April day when French and Algerian soldiers saw a greenish cloud rolling toward them. Over the next decades, the international community determined that such an attack could not be allowed. The result is that poison gas, chemical weapons, should be classed not as a weapon of war, but as a weapon of mass terror. That judgment was confirmed by the 1993 adoption of the Chemical Weapons Convention, signed by the U.S., Russia, China, India—and agreed to by Syria’s Bashar Assad under international pressure after the Ghouta attack of 2013.

President Trump was reportedly mystified by Assad’s decision to use sarin gas, and asked his advisers and friends for their best theories. Why would he make such a risky move? Perhaps the best explanation is that violating an international norm, one that was put in place by the world’s horrified reaction to that green cloud in Ypres, was precisely the point.

“Spreading terror is exactly what Assad wanted to do at Khan Shaykhun,” says Hassan Hassan, who tracks the Syrian conflict as a senior fellow at the Tahrir Institute of Middle East Policy. “The U.S. said the attack crossed any number of lines, and that’s right—Assad not only targeted civilians, he sent his own people a message: that they’re on their own, that the international community doesn’t care about them. The U.S. response showed that that’s not true.”

Just as crucially, Hassan says, the Trump administration’s response has put Russia on the defensive, uncomfortably defending an act that, because Moscow agreed to the 1993 treaty, is indefensible. “The Russians are really sensitive about this,” he says. “Which is why they’ve gone out of their way to claim that the weapons were actually being stored by the opposition. No one really believes that, and I’ll bet that they don’t, either.”